1. Choose the TWO correct statements describing the citrate cycle. ATP is an ind
ID: 94816 • Letter: 1
Question
1. Choose the TWO correct statements describing the citrate cycle.
ATP is an indirect product of the citric acid cycle
Acetyl CoA can increase the pool of citric acid cycle intermediates
Fatty acids can increase the pool of citric acid cycle intermediates
ADP inhibits -ketoglutarate dehydrogenase
The pool of mitochondrial oxaloacetate can be increased by pyruvate
All enzymes of the citric acid cycle are found soluble and free in the mitochondrial matrix
2.Which molecule in the net reaction of the citrate cycle contributes to the inhibition of pyruvate dehydrogenase?
NADH
H+
H2O
FAD
3. How would a high NADH to NAD+ ratio be expected to affect the pyruvate dehydrogenase reaction?
The E1 subunit is phosphorylated by pyruvate dehydrogenase kinase, and the catalytic activity of pyruvate dehydrogenase decreases.
The last step of the pyruvate dehydrogenase reaction is blocked, resulting in a decrease in activity.
The pyruvate dehydrogenase phosphatase-1 enzyme would increase, resulting in pyruvate dehydrogenase activation at an accelerated rate.
The pyruvate dehydrogenase kinase enzyme activity would increase, resulting in an increase in pyruvate dehydrogenase activity.
ATP is an indirect product of the citric acid cycle
Acetyl CoA can increase the pool of citric acid cycle intermediates
Fatty acids can increase the pool of citric acid cycle intermediates
ADP inhibits -ketoglutarate dehydrogenase
The pool of mitochondrial oxaloacetate can be increased by pyruvate
All enzymes of the citric acid cycle are found soluble and free in the mitochondrial matrix
Explanation / Answer
1.The pool of mitochondrial oxaloacetate can be increased by pyruvate.This stimulates respiration. Oxaloacetate is regenerated in the cycle, so addition of
oxaloacetate (or malate) stimulates the oxidation of a much larger amount of acetyl-CoA.
ATP is an indirect product of the citric acid cycle as This is the most important link to the electron transport chain where most of the ATP needed for energy reactions is produced.
2.The complex is strongly inhibited by ATP, as well as by acetyl-CoA and NADH, the products of the reaction .
3. The E1-catalyzed process is the rate-limiting step of the whole pyruvate dehydrogenase complex.
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